1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method of processing multi-valued image data corresponding to a predetermined area of a recording medium for recording an image in the predetermined area through a relative movement of the recording medium and a recording head.
2. Description of the Related Art
As a technology for suppressing density fluctuations and streaks of an image recorded in an inkjet recording apparatus, a multi-pass recording system is proposed for performing a recording scanning by a recording head by plural times with respect to a same area of a recording medium and completing an image that should be recorded on the above-mentioned same area. However, even when the multi-pass recording system is adopted, due to variations in a conveyance amount of the recording medium or the like, a shift may be generated between a dot recording position for a preceding recording scanning and a dot recording position for a succeeding recording scanning in some cases. Such a shift leads to variations in a dot coverage, and because of this, image adverse effects such as density variations and density fluctuations are generated.
As a technology for suppressing such image adverse effects, Japanese Patent Laid-Open No. 2000-103088 discloses a method of dividing image data so as to correspond to different recording scannings in a stage of multi-valued image data before binarization and independently binarizing each of the multi-valued image data after the division (in an uncorrelated manner). FIG. 10A shows an arrangement state of dots recorded on the basis of the image data processed through the method according to Japanese Patent Laid-Open No. 2000-103088. In the drawing, black circles 551 represents dots recorded by a first recording scanning, white circles 552 represents dots recorded by a second recording scanning, and gray circles 553 represents dots overlapped and recorded by the first recording scanning and the second recording scanning.
According to such a dot arrangement, even when the dot group recorded by the first recording scanning and the dot group recorded by the second recording scanning are shifted in a main scanning direction or a sub scanning direction, the coverage of the dots with respect to the recording medium do not vary so much. This is because parts where the dots recorded by the first recording scanning and the dots recorded by the second recording scanning are overlapped with each other also newly appear, but parts where two dots that should be originally overlapped and recorded are not overlapped with each other also exist.
However, according to the method disclosed in Japanese Patent Laid-Open No. 2000-103088, as the multi-valued data corresponding to the different recording scannings is quantized in an uncorrelated manner, the overlapping amount of mutual dots recorded by the different recording scannings cannot be controlled. Therefore, in some cases, the number of overlapping dots is excessive and a granularity of the image is deteriorated, and conversely, the number of overlapping dots is too small and the above-mentioned density variations cannot be sufficiently suppressed.